Bulk acoustic wave filters on shared die

ABSTRACT

Bulk acoustic wave resonators of two or more different filters can be on a common die. The two filters can be included in a multiplexer, such as a duplexer, or implemented as standalone filters. With bulk acoustic wave resonators of two or more filters on the same die, the filters can be implemented in less physical space compared to implementing the same filters of different die. Related methods, radio frequency systems, radio frequency modules, and wireless communication devices are also disclosed.

CROSS REFERENCE TO PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR § 1.57.This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 62/878,135, filed Jul. 24, 2019 and titled“METHOD FOR FORMING MULTIPLE BULK ACOUSTIC WAVE FILTERS ON SHARED DIE,”U.S. Provisional Patent Application No. 62/878,209, filed Jul. 24, 2019and titled “BULK ACOUSTIC WAVE FILTERS ON SHARED DIE,” and U.S.Provisional Patent Application No. 62/878,189, filed Jul. 24, 2019 andtitled “BULK ACOUSTIC WAVE FILTER CO-PACKAGE,” the disclosures of eachwhich are hereby incorporated by reference in their entireties herein.

BACKGROUND Technical Field

Embodiments of this disclosure relate to acoustic wave devices, forexample, bulk acoustic wave devices.

Description of Related Technology

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include one or more acoustic wave filters. A pluralityof acoustic wave filters can be arranged as a multiplexer. For instance,two acoustic wave filters can be arranged as a duplexer.

With the explosive growth of mobile communication, the frequencyspectrum is becoming crowded. This can generate demanding specificationsfor radio frequency (RF) filters and duplexers with steep roll-off, lowtemperature drift, low insertion loss, miniature size, the like, or anycombination thereof.

An acoustic wave filter can include a plurality of resonators arrangedto filter a radio frequency signal. Example acoustic wave filtersinclude surface acoustic wave (SAW) filters and bulk acoustic wave (BAW)filters. Example BAW resonators include film bulk acoustic waveresonators (FBARs) and solidly mounted resonators (SMRs). In BAWfilters, acoustic waves propagate in a bulk of a piezoelectric layer. ASAW filter can include an interdigital transductor electrode on apiezoelectric substrate and can generate a surface acoustic wave on asurface of the piezoelectric layer on which the interdigital transductorelectrode is disposed.

SUMMARY

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

One aspect of this disclosure is a multi-filter die with bulk acousticwave filters. The multi-filter die includes a first filter located in afirst region of a substrate and a second filter located in a secondregion of the substrate. The first filter includes a first plurality ofbulk acoustic wave resonators. The second filter includes a secondplurality of bulk acoustic wave resonators. At least one of the firstplurality of bulk acoustic wave resonators has the same resonantfrequency as at least one of the second plurality of bulk acoustic waveresonators.

The first and second filters can be included in a multiplexer. The firstand second filters can be electrically connected to one another at acommon contact by at least one electrical connection of the multi filterdie.

The multi-filter die can be free from electrical connections between thefirst filter and the second filter.

The first plurality of bulk acoustic wave resonators and the secondplurality of bulk acoustic wave resonators can be film bulk acousticwave resonators.

The first plurality of bulk acoustic wave resonators can each include araised frame structure.

The first filter can be a first band pass filter having a firstpassband, the second filter can be a second band pass filter having asecond passband, and the first passband can overlap with the secondpassband.

The first filter and the second filter can include a common materialstack. A thickness of a piezoelectric layer of the one of the firstplurality of bulk acoustic wave resonators can be the same as athickness of a piezoelectric layer of the one of the second plurality ofbulk acoustic wave resonators. A thickness of a lower electrode of theone of the first plurality of bulk acoustic wave resonators can be thesame as a thickness of a lower electrode of the one of the secondplurality of bulk acoustic wave resonators. The lower electrode of theone of the first plurality of bulk acoustic wave resonators can includea same material as the lower electrode of the one of the secondplurality of bulk acoustic wave resonators.

The first filter and the second filter can share a common frequencyrange.

Another aspect of this disclosure is a multi-filter die with bulkacoustic wave filters. The multi-filter die includes a first filterlocated in a first region of a substrate and a second filter located ina second region of the substrate. The first filter includes a firstplurality of bulk acoustic wave resonators. Each of the first pluralityof bulk acoustic wave resonators has a resonant frequency. The secondfilter includes a second plurality of bulk acoustic wave resonators.Each of the second plurality of bulk acoustic wave resonators has aresonant frequency. A difference between resonant frequencies of twobulk acoustic wave resonators of the first plurality of bulk acousticwave resonators is equal to a difference between resonant frequencies oftwo bulk acoustic wave resonators of the second plurality of bulkacoustic wave resonators.

In some instances, each of resonant frequencies of the first pluralityof bulk acoustic wave resonators can be different from each of theresonant frequencies of the second plurality of bulk acoustic waveresonators.

The first and second filters can be included in a multiplexer.

The multi-filter die can be free from electrical connections between thefirst filter and the second filter.

The first plurality of bulk acoustic wave resonators and the secondplurality of bulk acoustic wave resonators can be film bulk acousticwave resonators.

The first plurality of bulk acoustic wave resonators can each include araised frame structure.

The first filter can be a first band pass filter having a firstpassband, the second filter can be a second band pass filter having asecond passband, and the first passband can overlap with the secondpassband.

The first filter and the second filter can be formed using a commonmaterial stack.

The first filter and the second filter can share a common frequencyrange.

Another aspect of this disclosure is a radio frequency system thatincludes a radio frequency amplifier, a multi-filter die including afirst filter in a first region of a substrate and a second filter in asecond region of the substrate, and a switch configured to selectivelyelectrically connect the radio frequency amplifier and the first filter.The first filter includes a first plurality of bulk acoustic waveresonators. The second filter includes a second plurality of bulkacoustic wave resonators. At least one of the first plurality of bulkacoustic wave resonators has the same resonant frequency as at least oneof the second plurality of bulk acoustic wave resonators.

The radio frequency amplifier can be a power amplifier. Alternatively,the radio frequency amplifier can be a low noise amplifier.

Another aspect of this disclosure is a multi-filter die with bulkacoustic wave filters. The multi-filter die includes a first filtersupported by a substrate, the first filter including a first pluralityof bulk acoustic wave resonators, each of the first plurality of bulkacoustic wave resonators having one of a first plurality of resonantfrequencies; and a second filter located in a second region of thesubstrate, the second filter including a second plurality of bulkacoustic wave resonators, each of the second plurality of bulk acousticwave resonators having one of a second plurality of resonantfrequencies, the resonant frequencies of least a portion of the firstplurality of bulk acoustic wave resonators and at least a portion of thesecond plurality of bulk acoustic wave resonators having beenconcurrently adjusted by a common trimming process.

At least one of the first plurality of resonant frequencies can be equalto at least one of the second plurality of resonant frequencies. Adifference between a first resonant frequency and a second resonantfrequency of the first plurality of resonant frequencies can be equal toa difference between a first resonant frequency and a second resonantfrequency of the second plurality of resonant frequencies. None of thefirst plurality of resonant frequencies may be equal to any of thesecond plurality of resonant frequencies.

The first filter and the second filter can share a common frequencyrange.

The first filter and the second filter can be formed using a commonmaterial stack.

Another aspect of this disclosure is a multi-filter die with bulkacoustic wave filters. The multi-filter die includes: a first filterlocated in a first region of a substrate, the first filter including afirst plurality of bulk acoustic wave resonators; and a second filterlocated in a second region of the substrate, the second filter includinga second plurality of bulk acoustic wave resonators.

The first and second filters can be included in a multiplexer. The firstand second filters can be electrically connected to one another at acommon contact by at least one electrical connection internal to and/orsupported by the multi-filter die.

The multi-filter die can be free from electrical connections between thefirst and second filters. The first filter die can be in electricalcommunication with a first discrete input/output contact and a seconddiscrete input/output contact and the second filter can be in electricalcommunication with a third discrete input/output contact and a fourthdiscrete input/output contact.

The first filter and the second filter can share a common frequencyrange.

The first filter and the second filter can be formed by a process thatincludes at least one shared trimming step.

The first filter and the second filter can be formed using a commonmaterial stack.

Each of the first plurality of bulk acoustic wave resonators and each ofthe second plurality of bulk acoustic wave resonators can include apiezoelectric layer, an upper electrode, and a lower electrode, theupper electrode and the lower electrode located on opposite sides of thepiezoelectric layer. The piezoelectric layers of the first plurality ofbulk acoustic wave resonators can include the same piezoelectricmaterial as the piezoelectric layers of the second plurality of bulkacoustic wave resonators. A thickness of the piezoelectric layers of thefirst plurality of bulk acoustic wave resonators can be the same as athickness of the piezoelectric layers of the second plurality of bulkacoustic wave resonators. Lower electrodes of the first plurality ofbulk acoustic wave resonators can include the same material as the lowerelectrodes of the second plurality of bulk acoustic wave resonators. Athickness of the lower electrodes of the first plurality of bulkacoustic wave resonators can be the same as a thickness of the lowerelectrodes of the second plurality of bulk acoustic wave resonators.

The two filters can be co-packaged in a single package.

Another aspect of this disclosure is a method of tuning bulk acousticwave filters on a single die. The method includes: providing amulti-filter die including a first plurality of bulk acoustic waveresonators of a first filter and a second plurality of bulk acousticwave resonators of a second filter; and performing a shared trimmingstep that adjusts a resonant frequency of at least one of the firstplurality of bulk acoustic wave resonators and a resonant frequency ofat least one of the second plurality of bulk acoustic wave resonators.

The method can further include performing a second trimming step toadjust the resonant frequency of the at least one of the first pluralityof bulk acoustic wave resonators without affecting the resonantfrequencies of any of the second plurality of bulk acoustic waveresonators.

The method can further include performing a plurality of additionaltrimming steps to adjust the resonant frequencies of several of thefirst plurality of bulk acoustic wave resonators and several the secondplurality of bulk acoustic wave resonators to a plurality of discretetarget resonant frequencies. A total number of trimming steps performedcan be less than the number of the plurality of target resonantfrequencies. The total number of trimming steps performed can be atleast three fewer than the number of the plurality of discrete targetresonant frequencies.

The first plurality of bulk acoustic wave resonators and the secondplurality of bulk acoustic wave resonators can be film bulk acousticwave resonators. The first plurality of bulk acoustic wave resonatorscan include one or more bulk acoustic wave resonators having arespective raised frame structure.

The shared trimming step can adjusts the resonant frequency of the atleast one of the first plurality of bulk acoustic wave resonators bytrimming a portion of an upper electrode of the at least one of thefirst plurality of bulk acoustic wave resonators.

Another aspect of this disclosure is a method of tuning bulk acousticwave filters on a single die. The method includes forming a firstplurality of bulk acoustic wave resonators of a first filter on a die,each of the first plurality of bulk acoustic wave resonators having anassociated resonant frequency; forming a second plurality of bulkacoustic wave resonators of a second filter on the same die as the firstplurality of bulk acoustic wave resonators, each of the second pluralityof bulk acoustic wave resonators having an associated resonantfrequency; and performing a plurality of trimming steps to adjust atleast some of the resonant frequencies of the first and secondpluralities of bulk acoustic wave resonators, at least one of theplurality of trimming steps adjusting respective resonant frequencies ofat least one of the first plurality of bulk acoustic wave resonators andat least one of the second plurality of bulk acoustic wave resonators.

Performing the plurality of trimming steps can include adjusting theresonant frequencies of the first plurality of bulk acoustic waveresonators to a first plurality of target resonant frequencies andadjusting the resonant frequencies of the second plurality of bulkacoustic wave resonators to a second plurality of target resonantfrequencies. At least some of the first plurality of target resonantfrequencies can be equal to at least some of the second plurality oftarget resonant frequencies. A frequency differential between two of thefirst plurality of target resonant frequencies can be equal to afrequency differential between two of the second plurality of targetresonant frequencies. None of the first plurality of target resonantfrequencies may be equal to at least one of the second plurality oftarget resonant frequencies.

Each of the first plurality of bulk acoustic wave resonators can includea piezoelectric layer, an upper electrode, and a lower electrode, theupper electrode and the lower electrode located on opposite sides of thepiezoelectric layer. The first trimming step can adjusts the resonantfrequency of the at least one of the first plurality of bulk acousticwave resonators by trimming a portion of the upper electrode of the atleast one of the first plurality of bulk acoustic wave resonators.

Another aspect of this disclosure is a method of forming a packageincluding a multi-filter die. The method includes performing a sharedtrimming step on a first filter and a second filter of a multi-filterdie, the first filter including a first plurality of bulk acoustic waveresonators and the second filter including a second plurality of bulkacoustic wave resonators, the shared trimming step adjusting a resonantfrequency of at least one of the first plurality of bulk acoustic waveresonators of the first filter and adjusting an resonant frequency of atleast one of the second bulk acoustic wave resonators of the secondfilter; forming at least one electrical connection between themulti-filter die and a package substrate supporting the multi-filterdie; and encapsulating the multi-filter die in a package.

The method can further include performing a plurality of additionaltrimming steps to adjust the resonant frequencies of several of thefirst plurality of bulk acoustic wave resonators and several of thesecond plurality of bulk acoustic wave resonators to a first pluralityof discrete target resonant frequencies of the first plurality of bulkacoustic wave resonators and a second plurality of discrete targetresonant frequencies of the second plurality of bulk acoustic waveresonators. At least one of the discrete target resonant frequencies ofthe first plurality of bulk acoustic wave resonators can be equal to atleast one of the discrete target resonant frequencies of the secondplurality of bulk acoustic wave resonators.

The method can further include performing a plurality of additionaltrimming steps to adjust the resonant frequencies of a portion of thefirst plurality of bulk acoustic wave resonators and a portion of thesecond plurality of bulk acoustic wave resonators to a first pluralityof discrete target resonant frequencies of the first plurality of bulkacoustic wave resonators and a second plurality of discrete targetresonant frequencies of the second plurality of bulk acoustic waveresonators. A resonant frequency of at least one of the first pluralityof bulk wave resonators may not be adjusted by a trimming step. Adifference between a first discrete target resonant frequency and asecond discrete target resonant frequency of the first plurality ofdiscrete target resonant frequencies of the first plurality of bulkacoustic wave resonators is equal to a difference between a firstdiscrete target resonant frequency and a second discrete target resonantfrequency of the second plurality of discrete target resonantfrequencies of the second plurality of bulk acoustic wave resonators.None of the first plurality of discrete target resonant frequencies ofthe first plurality of bulk acoustic wave resonators may be equal to oneof the second plurality of discrete target resonant frequencies of thesecond plurality of bulk acoustic wave resonators.

Another aspect of this disclosure is a multi-filter package thatincludes a multi-filter die including a first filter and a secondfilter, a packaging substrate supporting the multi-filter die, and apackaging structure attached with the substrate. The first filterincludes at least one bulk acoustic wave resonator. The packagingstructure and the packaging substrate together form a packageencapsulating the multi-filter die.

The second filter can include at least one bulk acoustic wave resonator.The one bulk acoustic wave resonators of the first filter and the onebulk acoustic wave resonator of the second filters can have respectiveresonant frequencies that are equal to each other. The one bulk acousticwave resonators of the first filter and the one bulk acoustic waveresonator of the second filters can have be formed in a process thatincludes a shared trimming step. The bulk acoustic wave resonator of thefirst filter is can be electrical communication with the bulk acousticwave resonator of the second filter by way of a conductive structuresupported by the multi-filter die.

The first filter and the second filter can share a common input/outputport.

The multi-filter package can further include first and second internalinterconnect structures in electrical communication with the firstfilter and third and fourth internal interconnect structures inelectrical communication with the second filter. The first and thirdinternal interconnect structures can be in electrical communication withone another by way of a conductive structure internal to the package.The conductive structure internal to the package can be supported by themulti-filter die. The conductive structure internal to the package canbe supported by the packaging substrate.

Another aspect of this disclosure is a package encapsulating multiplebulk acoustic wave filters. The package includes a packaging substrate;a first filter die supported by the packaging substrate and including afirst bulk acoustic wave filter, the first bulk acoustic wave filterincluding at least one bulk acoustic wave resonator; a second filter diesupported by the packaging substrate and including a second bulkacoustic wave filter, the second bulk acoustic wave filter including atleast one bulk acoustic wave resonator; and a cover sealed to thepackaging substrate and that together with the packaging substrate formsa package encapsulating the first and second filter dies.

The first bulk acoustic wave filter can have a different frequency rangethan the second bulk acoustic wave filter.

The first filter and the second filter can be formed using differentmaterial stacks.

Each of the at least one bulk acoustic wave resonator of the first bulkacoustic wave filter and the at least one bulk acoustic wave resonatorof the second bulk acoustic wave filter can include a piezoelectriclayer, an upper electrode, and a lower electrode, the upper electrodeand the lower electrode located on opposite sides of the piezoelectriclayer. A thickness of the piezoelectric layer of the at least one bulkacoustic wave resonator of the first bulk acoustic wave filter can bedifferent from a thickness of the piezoelectric layer of the at leastone bulk acoustic wave resonator of the second bulk acoustic wavefilter. A thickness of the lower electrode of the at least one bulkacoustic wave resonator of the first bulk acoustic wave filter can bedifferent from a thickness of the lower electrode of the at least onebulk acoustic wave resonator of the second bulk acoustic wave filter.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1 is a cross sectional view illustrating a single packagecontaining two bulk acoustic wave (BAW) filters on separate chipsaccording to one embodiment.

FIG. 2A is a cross sectional view illustrating a single substratesupporting two BAW resonators according to an embodiment.

FIG. 2B is a cross sectional view of a portion of one of the BAWresonators of FIG. 2A.

FIG. 3A is a cross sectional view illustrating a single packagecontaining two bulk acoustic wave (BAW) filters on a single chipaccording to an embodiment.

FIG. 3B is a top plan view schematically illustrating two co-packagedBAW filters having a shared input/output according to anotherembodiment.

FIG. 3C is a cross sectional view of single package containing two bulkacoustic wave (BAW) filters on a single chip with a shared input/outputon the chip according to another embodiment.

FIG. 4A is a cross sectional view illustrating a single packagecontaining two bulk acoustic wave (BAW) filters on a single chipaccording to another embodiment.

FIG. 4B is a top plan view schematically illustrating two co-packagedBAW filters having distinct inputs and outputs according to anotherembodiment.

FIG. 4C is a cross sectional view illustrating a single packagecontaining two bulk acoustic wave (BAW) filters on a single chip and anadditional filter on a second chip according to another embodiment.

FIG. 5 is a cross sectional view illustrating a single substratesupporting a BAW resonator and a surface acoustic wave (SAW) resonatoraccording to another embodiment.

FIG. 6 is a cross sectional view illustrating a single substratesupporting two BAW resonators having different resonant frequenciesaccording to another embodiment.

FIGS. 7A through 7F illustrate cross-sections of a portion of two BAWresonators at various stages of a manufacturing process including ashared trimming step according to another embodiment.

FIG. 8 is a flow diagram schematically illustrating certain steps in aprocess for trimming two BAW resonators on a single substrate includinga shared trimming step in another embodiment.

FIGS. 9A through 9I illustrate cross-sections of a portion of three BAWresonators at various stages of a manufacturing process including twoshared trimming steps according to another embodiment.

FIG. 10 is a flow diagram schematically illustrating certain steps in aprocess for trimming three BAW resonators on a single substrateincluding two shared trimming steps in another embodiment.

FIG. 11A is a top plan view schematically illustrating two BAW filters,each including a plurality of BAW resonators.

FIG. 11B is a top plan view schematically illustrating two BAW filtersthat are co-packaged and that each have a BAW resonators with the sameresonant frequency.

FIG. 11C is a top plan view schematically illustrating two BAW filtersthat are co-packaged and that each have two BAW resonators with the samedifferential in resonant frequency.

FIG. 12 is a schematic diagram of a radio frequency module that includesa filter with BAW resonators according to an embodiment.

FIG. 13 is a schematic diagram of a radio frequency module that includesduplexers with BAW resonators according to an embodiment.

FIG. 14A is a schematic block diagram of a module that includes a poweramplifier, a radio frequency switch, and duplexers that include one ormore BAW resonators according to an embodiment.

FIG. 14B is a schematic block diagram of a module that includes a lownoise amplifier, a radio frequency switch, and bulk acoustic wavefilters according to an embodiment.

FIG. 15 is a schematic block diagram of a module that includes anantenna switch and duplexers that include one or more BAW resonatorsaccording to an embodiment.

FIG. 16A is a schematic block diagram of a wireless communication devicethat includes a BAW filter in accordance with one or more embodiments.

FIG. 16B is a schematic block diagram of another wireless communicationdevice that includes a BAW filter in accordance with one or moreembodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings, where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

With reduced module sizes and specifications for better performance, itis becoming increasingly difficult to achieve desirable filterperformance and be cost effective while reducing the size of filters.While a plurality of surface acoustic wave (SAW) filters can be includedon a single die by virtue of the lithographic definition of the metalfingers of the interdigital electrodes, one bulk acoustic wave (BAW)filter is typically included on a single die, as the various materialthicknesses of the layer stack of the BAW filter can largely determinethe filter performance parameters.

Aspects of this disclosure relate to co-packaging two or more distinctBAW filters on a single die. The two or more BAW filters can be includedin a multiplexer, such as a duplexer, or implemented as standalonefilters. Multiple BAW filters on one die for a common frequency rangecan use the same stack and hence can be co-packaged on one die. Such BAWfilters can meet different performance specifications. Multiple BAWfilters having passbands that are relatively close together in frequencycan use the same stack and be trimmed differently for co-packaged die.In some instances, BAW band pass filters having passbands that overlapcan be implemented on a common die. While having the same stack can beadvantageous for co-packaging, multiple stacks can alternatively oradditionally be implemented. The same trimming masks can be used formultiple BAW resonators across different filters on the same die toachieve different frequencies for resonators. This can allow the designsto be more flexible and complex while also reducing mask costs.

In some instances, one or more BAW filters can be co-packaged with oneor more other technologies on the same die. For example, one or more BAWfilters can be co-packaged with one or more SAW filters and/or one ormore filters that include Lamb wave resonators. As another example, twoor more BAW filters can be co-packaged with one or more SAW filtersand/or one or more filters that include Lamb wave resonators. Anysuitable principles and advantages disclosed herein can be applied tofilters that include two or more types of acoustic wave resonators (forexample, a filter with at least one BAW resonator and at least one SAWresonator). Any suitable principles and advantages disclosed herein canbe applied to filters that include acoustic wave resonators andinductor-capacitor components (for example, a filter with at least oneBAW resonator, one or more inductors, and one or more capacitors).

Packaging more than one bulk acoustic wave (BAW) filter on the same diein a single package may allow for a reduction in the overall size of thepackaging for those filters. Where multiple BAW filters are provided ona single die, and co-packaged together, the time and cost involved infabricating the BAW filters can also be reduced through the use ofshared processing steps. In particular, the BAW filters may be designedso that shared trimming steps between BAW resonators of the differentfilters on the single die can reduce the overall number of trimmingsteps involved in the fabrication of the BAW filters. This can alsoreduce a number of masks that are fabricated for manufacturing BAWfilters. BAW filters may also be co-packaged with one or more acousticwave filters of a different type.

FIG. 1 is a cross sectional view illustrating a single packagecontaining two bulk acoustic wave (BAW) filters on separate chipsaccording to one embodiment. The package 100 includes a cover 180secured to a supporting structure including a packaging substrate 190 bya bond 182 extending around the periphery of the cover 180. The package100 together with the components packaged therein can be referred to asa packaged component. The illustrated packaging substrate 190 is amulti-layer packaging substrate that includes first and second layers190 a and 190 b, respectively. The cover 180 has a recessed portion inwhich a first die 110 a and a second die 110 b are located.

The first die 110 a may include a first BAW filter, and the second die110 b may include a second BAW filter. In the illustrated embodiment,the cover 180 together with the supporting structure including packagingsubstrate 190 to encapsulate the first and second dies 110 a and 110 bthat include the first and second BAW filters, respectively. Althoughdescribed as including BAW filters, in some other embodiments, one orboth of the dies 110 a and 110 b may include other acoustic wavefilters, such as a SAW filter and/or Lamb wave resonator filter and/or afilter that includes two different types of acoustic wave devices, inplace of or in addition to the BAW filter. One or more BAW filtersenclosed by the package 100 can be electrically connected to one or morecircuit elements that are external to the package 100 such as one ormore other filters of a multiplexer, one or more passive circuitelements (such as one or more inductors and/or one or more capacitors),one or more radio frequency switches, one or more amplifiers (such asone or more power amplifiers or one or more low noise amplifiers), orany suitable combination thereof.

Connection with the first and second dies 110 a and 110 b in theinterior of package 100 is provided by external interconnect structures192 a, 192 b, and 192 c extending through packaging substrate 190. Asillustrated, these external interconnect structures may include viasextending through each of packaging substrate layers 190 a and 190 b.Some or all of the vias extending through the second packaging substratelayer 190 b may be offset from a corresponding via extending through thefirst packaging substrate layer 190 a to which it is connected, and aconnected trace or other conductive structure located between the firstpackaging substrate layer 190 a and the second packaging substrate layer190 b. The use of such offset vias allows the exposed external ends ofthe external interconnect structure to be spaced farther apart from oneanother than the internal connections and/or at desired locations, whichmay assist in the formation of electrical connections with the package100.

Within the package 100, internal interconnect structures 112 a and 114 aprovide electrical connections with first die 110 a, These connectionsmay represent, for example, an input and an output of the filter onfirst die 110 a. Similarly, internal interconnect structures 112 b and114 b provide electrical connections with second die 110 b. Theseinterconnect structures 112 a, 112 b, 114 a, and 114 b may be formed,for example, by soldering or otherwise connecting bond pads or otherconductive structures on the interior surface of packaging substrate 190to bond pads or other conductive structures on facing surfaces of firstand second dies 110 a and 110 b.

In the illustrated embodiment, interconnect structure 112 b is inelectrical communication with interconnect structure 114 a, via aconductive trace or other structure on the interior surface of packagingsubstrate 190. This connection may provide an electrical connection,internal to the package 100, between the filter on the first die 110 aand the second die 110 b. In some other embodiments, an internalconnection may be provided using a conductive structure located betweenfirst packaging substrate layer 190 a and second packaging substratelayer 190 b. In some other embodiments, a package may have no internalconnection between the dies 110 a and 110 b, and any desired connectionmay be formed through external connections, which may be formed orotherwise provided after the package 100 is sealed.

In some embodiments, rather than packaging two or more individual dies,each supporting a single BAW filter or another filter, a multi-filterdie may be provided and packaged. FIG. 2A is a cross sectional viewillustrating a single substrate supporting two BAW resonators accordingto an embodiment. FIG. 2B is a zoomed in cross sectional view of aportion of one of the BAW resonators of FIG. 2A. In the illustratedembodiment, the BAW resonators 220 a and 220 b are formed on a singlesubstrate 202, which may be a silicon substrate or a support substrateof any other suitable material. The BAW resonators 220 a and 220 b canbe included in different filters. Accordingly, FIG. 2A illustrates BAWresonators of different filters on a common die. Additional resonatorsmay also be provided on the substrate, although such additionalresonators are not depicted in FIG. 2A.

In the filter assembly 200 illustrated in FIG. 2A, the BAW resonators220 a and 220 b are similar in structure and design to one another. Withsufficient similarity between the BAW resonators 220 a and 220 b, thesame material stack may be used to form the BAW resonators 220 a and 220b, increasing the efficiency of the fabrication process by allowingsimultaneous fabrication of multiple resonators. In some otherembodiments, however, the BAW resonators 220 a and 220 b may be formedusing manufacturing processes which differ from one another with respectto at least one step or material, such that only a portion of thefabrication steps and/or materials may be shared between the BAWresonators 220 a and 220 b. In some other embodiments, the fabricationprocesses for the first and second BAW resonators 220 a and 220 b may beentirely distinct from one another.

As illustrated, the BAW resonators 220 a and 220 b are film bulkacoustic wave resonators (FBARs), and are partially spaced apart fromthe underlying substrate 202 by an air gap or cavity 228. This cavity228 may be formed, for example, by depositing or otherwise forming asacrificial layer or layers in a desired shape prior to the formation ofoverlying layers of the BAW resonators 220 a and 220 b, and subsequentlyremoving the sacrificial layer or layers at a later stage of thefabrication process. Alternatively, an air cavity can be etched into thesubstrate 202 in certain instances (not illustrated in FIG. 2A). In someother embodiments, the BAW resonators may be solidly mounted resonatorswithout such a cavity 228. In such embodiments, the BAW resonators mayinstead include an acoustic Bragg reflector. Such an acoustic Braggreflector may be used in place of or in addition to one or morecavities, depending on the design of the particular BAW resonator. Theembodiments described herein may be suitable for use with BAW resonatorsof any suitable type or design, and any suitable combination of suchresonators.

The BAW resonators 220 a and 220 b include a lower electrode 240 and anupper electrode 250, separated from one another by a piezoelectric layer230. The piezoelectric layer 230 can be an aluminum nitride (AlN) layeror any other suitable piezoelectric layer. Portions of the piezoelectriclayer 230 and the lower and upper electrodes 240 and 250 extend over thecavity 228. At least a portion of the upper electrode 250 can bepatterned to adjust the resonant frequency of the BAW resonators 220 aand 220 b. An active region or active domain of a bulk acoustic waveresonator can be defined by the portion of the piezoelectric layer 230that overlaps and is in contact with both the upper electrode 250 andthe second electrode 240 over the cavity 228. In the embodiment shown inFIGS. 2A and 2B, the lower and upper electrodes 240 and 250,respectively, overlap for a significant portion of the illustratedpiezoelectric layer 230. The portions of these layers within the activeregion of the BAW resonators 220 a and 220 b may be substantiallyparallel to the underlying surface of the substrate 202.

Additional layers not explicitly illustrated in FIGS. 2A and 2B may alsobe included, such as passivation layers. A passivation layer may beprovided, for example, between the sacrificial layer and the otherlayers of the BAW resonator to protect those layers from the fabricationsteps used in the removal of the sacrificial layer. Such a passivationlayer can be present in a bulk acoustic wave device after removal of thesacrificial material. Similarly, a passivation layer may be providedover the upper surfaces of the layers of the BAW resonator.

As can be seen in the detail view of FIG. 2B, a portion of the upperelectrode 250 overlying the piezoelectric layer 230 includes a thinnercentral section 254 surrounded by a raised frame structure including afirst raised frame section 252 a and a second raised frame section 252b. Although described as two raised frame sections 252 a and 252 b inthe context of the cross-sectional view of FIGS. 2A and 2B, the raisedframe may extend in a contiguous manner around the periphery of thecentral section 254. Such a raised frame can have an annular shape inplan view. The portion of the BAW resonator including the raised framestructure may be referred to as the raised frame zone or as a borderring. The thinner central section 254 may be recessed by a distance 256.The raised frame structure can block lateral energy leakage from theactive area of the BAW resonators 220 a or 220 b. In some embodiments, aBAW resonator may include two or more raised frame zones. Alternativelyor additionally, a BAW resonator can include one or more recessed framezones in which an upper electrode is thinner than in the active regionof the BAW resonator.

The BAW resonators 220 a and 220 b may be electrically connected to oneanother, or to other resonators supported by the substrate 202, by wayof any suitable conductive structure. In some embodiments, connectionsbetween resonators may include interconnect traces or other structuresformed on the same side of the substrate 202 as the resonators. In someembodiments, connections between resonators, or to external components,may include conductive vias extending into or through the substrate 202.

The BAW resonator 220 a may form a part of a first filter supported bysubstrate 202, and the BAW resonator 220 b may form a part of a secondfilter supported by substrate 202. Suitable interconnections between thefilters on substrate 202, if desired, may also be formed by any suitableconductive structure. The BAW resonators 220 a and 220 b can be includedin different filters and have the same resonant frequency.

FIG. 3A is a cross sectional view illustrating a single packagecontaining two bulk acoustic wave (BAW) filters on a single chipaccording to an embodiment. The package 300 includes a cover 380 securedto a packaging substrate 390 including packaging substrate layers 390 aand 390 b by a bond 382 extending around the periphery of the cover 380.The cover 380 has a recessed portion in which a multi-filter die 310 islocated. The multi-filter die 310 includes a first BAW filter and asecond BAW filter. Cover 380 together with the supporting structure 390including packaging substrate layers 390 a and 390 b encapsulates themulti-filter die 310, which includes the first and second BAW filters.Although described as including BAW filters, in some other embodimentsone or more of the filters of the multi-filter die 310 may be anacoustic wave filter of another type, such as a SAW filter.Alternatively or additionally, one or more filters of the multi-filterdie 310 can include two types of acoustic wave resonators, such as a BAWresonator and a SAW resonator. Moreover, although some description iswith reference to two BAW filters for illustrative purposes, anysuitable principles and advantages disclosed herein can be applied toapplications with three or more BAW filters.

External interconnect structures 392 a, 392 b, and 392 c extendingthrough packaging substrate layers 390 a and 390 b provide electricalconnections with the filters of the multi-filter die 310 in the interiorof package 300. Within the package 300, internal interconnect structures312 a, 312 b, 314 a, and 314 b provide electrical connections with themulti-filter die 310. These connections may represent input/outputs ofthe filters on multi-filter die 310.

In the illustrated embodiment, internal interconnect structure 312 b isin electrical communication with internal interconnect structure 314 a,via a conductive trace or other structure on the interior surface ofpackaging substrate layer 390 a. This connection may provide anelectrical connection, internal to the package 300, between two filterson multi-filter die 310. In some other embodiments, an internalconnection may be provided on or in the multi-filter die 310 itself. Insuch instances, the multi-filter die 310 can include a commoninput/output contact shared by the two BAW filters. Such an embodimentis described with respect to FIG. 3C.

FIG. 3B is a top plan view schematically illustrating two co-packagedBAW filters having a shared input/output contact according to anotherembodiment. Because the BAW filters 320 a and 320 b are co-packagedwithin a single package 300′, the packaging area 384 surrounding the BAWfilters 320 a and 320 b need not extend between the two filters 320 aand 320 b, which should reduce the overall size of the package 300′ incomparison to separately packaging filters 320 a and 320 b.

The first BAW filter 320 a on the shared multi-filter die 310 has adiscrete input/output 322 a, and the second BAW filter 320 b on theshared multi-filter die 310 has a discrete input/output 322 b. A sharedinput/output 324 is also provided. In some embodiments, the sharedinput/output 324 may be a shared output, and the filters may havediscrete inputs 322 a and 322 b. In some embodiments and/or modes, theshared input or output 324 may be a shared output, and the filters mayhave discrete inputs 322 a and 322 b. In some embodiments and/or modes,the shared input/output 324 may serve as an input to one filter, and anoutput to the other filter. The shared input/output 324 can be an inputfor one mode (e.g., receiving) and an output for another mode (e.g.,transmitting).

FIG. 3C is a cross sectional view of single package containing two bulkacoustic wave (BAW) filters on a single chip with a shared input/outputon the chip. Instead of the four internal structures of FIG. 3A, theillustrated package 300″ of FIG. 3C includes only three internalinterconnect structures, corresponding to a shared input/output 324 anddiscrete input/outputs 322 a and 322 b of the multi-filter die 310. Thetwo BAW filters of the package 300″ can be included in a duplexer. Theshared input/output can be a common node of the duplexer. The principlesand advantages of the embodiment of FIG. 3C for a duplexer can beapplied to other multiplexers, such as a quadplexer, a hexaplexer, etc.

FIG. 4A is a cross sectional view illustrating a single packagecontaining two bulk acoustic wave (BAW) filters on a single chipaccording to another embodiment. The illustrated package 400 includes acover 480 secured to a supporting structure 490 including packagingsubstrates 490 a and 490 b by a bond 482 extending around the peripheryof the cover 480. The cover 480 has a recessed portion in which amulti-filter die 410 is located. The multi-filter die 410 includes afirst BAW filter and a second BAW filter. In contrast to the filters ofthe packages in FIG. 3A and FIG. 3C, in which the filters on themulti-filter die are electrically connected to one another by aconnection internal to the package or internal to the multi-filter dieitself, the filters on the multi-filter die 410 are shown as not beingelectrically connected to one another within the packaged 400. Cover 480together with the supporting structure of a package substrate 490including packaging substrate layers 490 a and 490 b encapsulates thefirst and multi-filter die 410, which includes the first and second BAWfilters. Although described as including BAW filters, in some otherembodiments one or more of the filters of the multi-filter die 410 maybe an acoustic wave filter of another type, such as a SAW filter.Alternatively or additionally, one or more filters of the multi-filterdie 410 can include two types of acoustic wave resonators, such as a BAWresonator and a SAW resonator. In some embodiments, two co-packagedfilters, including two co-packaged filters on the multi-filter die 410,may be filters which are not used at the same time. For example, if thetwo filters are part of different multiplexers, there may be periods oftime during which one multiplexer is being used, and the other is not,such that only one of the two filters is being used at a given time.

External interconnect structures 492 a, 492 b, 492 c, and 492 dextending through packaging substrate layers 490 a and 490 b provideelectrical connections with the filters of the multi-filter die 410 inthe interior of package 400. Within the package 400, internalinterconnect structures 412 a, 412 b, 414 a, and 414 b provideelectrical connections with the multi-filter die 410. These connectionsmay represent input/outputs of the filters on multi-filter die 410. Inthe illustrated embodiment, each of the internal interconnect structures412 a, 412 b, 414 a, and 414 b provide discrete electrical connectionswith respective external interconnect structures 492 a, 492 b, 492 c,and 492 d.

FIG. 4B is a top plan view schematically illustrating two co-packagedBAW filters 420 a and 420 b having distinct input/outputs according toanother embodiment.

The first BAW filter 420 a on the shared multi-filter die 410 has afirst discrete input/output 422 a and a second discrete input/output 424a, and the second BAW filter 420 b on the shared multi-filter die 410has a first discrete input/output 422 b and a second discreteinput/output 424 b. Packaging area 484 is included around the BAWfilters 420 a and 420 b along a perimeter of the shared multi-filter die410. Because the BAW filters 420 a and 420 b are co-packaged within asingle package 400′, the packaging area 484 surrounding the BAW filters420 a and 420 b need not extend between the two filters 420 a and 420 b.This can reduce the overall size of the package 400′ in comparison toseparately packaging filters 420 a and 420 b.

Additional dies can be included on the same substrate as a multi-filterdie. FIG. 4C is a cross sectional view illustrating a single package400″ containing two bulk acoustic wave (BAW) filters on a single chipand an additional filter on a second chip. In addition to themulti-filter die 410, which includes at least first and second BAWfilters, an additional filter die 470, having associated internalinterconnects 412 c and 414 c connected to external interconnects 492 eand 492 f. The multi-filter die 410 can include any suitable combinationof features of the multi-filter die 410 of FIG. 4A and/or FIG. 4B. Insome embodiments, the additional filter die 470 may include at least onefilter of another type, such as a surface acoustic wave (SAW) filter ora Lamb wave filter. In other embodiments, the additional filter 470 diemay include an additional BAW filter, which may be of a design differentin materials or design from the BAW filters of the multi-filter die 410.

In some embodiments, a BAW resonator may be provided on a single dietogether with an acoustic resonator of another type. FIG. 5 is a crosssectional view illustrating a single substrate supporting a BAWresonator and a surface acoustic wave (SAW) resonator according toanother embodiment. The BAW resonator and the SAW resonator can beincluded on a shared die. The shared die can be implemented inaccordance with any suitable principles and advantages disclosed herein.For example, the shared die can include BAW resonators of two differentfilters and an SAW resonator. The SAW resonator can be included in athird filter in certain instances. Alternatively, the SAW resonator canbe included in one of the two different filters that include BAWresonators.

In the illustrated filter assembly 500 of FIG. 5, a BAW resonator 520 issupported by a substrate 502, along with a SAW resonator 570. The BAWresonator 510 includes an upper electrode 550 and a lower electrode 540,spaced apart from one another by a piezoelectric layer 530. A portion ofthe upper electrode 550, lower electrode 540, and piezoelectric layer530 are spaced apart from the substrate 502 by a cavity 528.

At another location of the substrate 502, a SAW resonator 570 issupported. The SAW resonator 570 may include a piezoelectric layer 572supported by the substrate 502. On the opposite side of thepiezoelectric layer 572 from the substrate 502 is an interdigitaltransducer electrode 574. The SAW resonator 570 may also includeadditional layers not explicitly depicted in FIG. 5. For example, theinterdigital transducer electrode 574 may be a multilayer structure,including at least two different conductive materials in a stack. TheSAW resonator 570 may be a temperature-compensated SAW resonator, andmay include a temperature compensation layer located over theinterdigital transducer electrode 574, such as a silicon dioxide (SiO₂)layer. In some other instances, the SAW resonator 570 can be amulti-layer piezoelectric substrate SAW resonator including one or moreadditional layers positioned between the substrate 502 and thepiezoelectric layer 570.

In some embodiments, at least some of the layers of the SAW resonator570 may include materials which are common to the BAW resonator 520. Forexample, the piezoelectric layer 530 of the BAW resonator 520 mayinclude the same material as the piezoelectric layer 572 of the SAWresonator 570. Similarly, the upper electrode 550 or the lower electrode540 of the BAW resonator 520 may include the same material as theinterdigital transducer electrode 574 of the SAW resonator 570.

In some embodiments, the BAW resonator 520 may form a part of a firstfilter, and the SAW resonator 570 may form a part of a second filtersupported by the same substrate 502 as the first filter. In someembodiments, the BAW resonator 520 may form a part of the same filter asthe SAW resonator 570. In some further embodiments, a second filterincluding other acoustic wave resonators may be formed on the samesubstrate. In addition, although not explicitly illustrated in FIG. 5,interconnect electrodes that provide electrical communication with otherresonators on the substrate 502 to form filter structures may also beprovided.

In some other embodiments, other types of acoustic wave resonators maybe supported by the substrate 502, in addition to or in place of SAWresonator 570. In some embodiments, the substrate 502 may support both aBAW resonator and a Lamb wave resonator.

In contrast to the wafer of FIG. 2A, in which the illustrated BAWresonators are similar in structure and design, wafers may also beprovided which support BAW resonators which are distinct in structureand/or design from one another. Despite these differences, manufacturingefficiencies may be realized in forming multiple BAW resonators on acommon substrate, even when the final designs of those BAW resonatorsare different from one another.

FIG. 6 is a cross sectional view illustrating a single substrate 602supporting two BAW resonators 620 a and 620 b having different resonantfrequencies according to another embodiment. The BAW resonators 620 aand 620 b can be included in different respective filters andimplemented on a single die. Other BAW resonators and/or other types ofacoustic wave resonators can be implemented on the single die. In theillustrated filter assembly 600, the first BAW resonator 620 a issimilar in structure and design to the second BAW resonator 620 b,except for the profile of the upper electrode 650 a of first BAWresonator 620 a and upper electrode 650 b of second BAW resonator 620 b.The thickness of the upper electrode 650 a of first BAW resonator 620 ain a central region is thinner than the thickness of the upper electrode650 b of second BAW resonator 620 b in a central region. This differencein thickness of portions of the upper electrodes 650 a and 650 b canaffect the resonant frequency of the first and second BAW resonators 620a and 620 b, respectively.

Although the other components of the first and second BAW resonators 620a and 620 b in the illustrated are similar in structure and design toone another, in other embodiments, there may be additional distinctionsin the structure or design of the BAW resonators. For example, in someembodiments, certain layers of the first and second BAW resonators 620 aand 620 b may differ in composition or thickness from one another, oradditional layers or components may be included in one of the first andsecond BAW resonators 620 a and 620 b and not included in the other.Even in such embodiments, common processing steps and/or materialsbetween the first and second BAW resonators 620 a and 620 b may makefabrication of both resonators on a single substrate more efficient thanfabricating those resonators on separate substrates.

In an embodiment in which two or more BAW filters having different layerstacks are formed on a substrate, the layer stacks may include uniquelayers which differ from a corresponding layer in the other layer stack.These unique layers may differ from one another with respect to thethickness of at least one unique layer, and/or with respect to thecomposition of at least one unique layer. In some embodiments, the twoor more BAW filters may be formed in entirely separate fabricationprocesses, while in other embodiments, at least some fabrication stepsmay be common between more than one BAW filter on the substrate.

In some particular embodiments, two or more BAW filters formed on asubstrate may each include at least one unique layer having a propertynot shared with a layer of another BAW filter, but other layers of thelayer stacks of the BAW filters may be common to each BAW filter. Insuch an embodiment, at least some the shared layers may be formed incommon fabrication steps, while the unique layers may be formed inseparate steps for each BAW filter, or using at least one uniquefabrication step.

In an embodiment where one of the unique layers of one BAW filterdiffers from one of the unique layers of a different BAW filter only inthickness, but includes the same material, a shared fabrication step maybe used between filters, while a further unique fabrication step may beapplied only to one of the filters. For example, in some embodiments, agiven layer of a first BAW filter layer stack is thicker than acorresponding layer of a second BAW filter layer stack. In one specificembodiment, layers of thickness equal to the thinner of the two layersmay be formed in both layer stacks, and an additional layer of athickness equal to the difference between the thickness of the thickerlayer and the thickness of the thinner layer may be formed only in thefirst BAW filter layer stack. In another embodiment, layers of thicknessequal to the thicker of two layers may be formed in both layer stacks,and that layer of the second BAW filter layer stack may be trimmed orotherwise reduced in thickness until a sufficiently thin layer isformed.

In an embodiment in which BAW resonators formed on a single substratediffer from one another at least in the design of their upperelectrodes, common trimming steps may be used to reduce the number oftrimming steps required to form such resonators. This efficiencyincrease may be more pronounced in an embodiment in which multiplefilters are formed on a single substrate, as the use of common trimmingsteps across resonators of multiple filters can reduce the total numberof processing steps used to form a multi-filter structure.

FIGS. 7A through 7F illustrate cross-sections of a portion of two BAWresonators at various stages of a manufacturing process including ashared trimming step according to another embodiment. These BAWresonators can be included in different filters on the same multi-filterdie. FIG. 7A is a cross-section of a first BAW resonator 720 a includingan upper electrode 750 a overlying a portion of a piezoelectric layer730 a. Also shown in FIG. 7A is a zoomed in view of a portion of theupper electrode 750 a. FIG. 7B is a cross-section of a second BAWresonator 720 b supported by the same substrate as the substratesupporting the first BAW resonator 720 a. The second BAW resonatorincludes an upper electrode 750 b overlying a portion of a piezoelectriclayer 730 b. FIG. 7B also includes a zoomed in view of a portion of theupper electrode 750 a. FIGS. 7A and 7B illustrate that that the upperelectrodes 750 a and 750 b are formed with an initial thickness T₀.

FIGS. 7C and 7D are cross-sections of the BAW resonators 720 a and 720b, respectively, after a first trimming step. FIG. 7C shows that thefirst trimming step has reduced the thickness of a central region 754 a′of the upper electrode 750 a of the first BAW resonator 720 a, whileleaving the thickness of a frame region of the upper electrode 750 asurrounding the central region 754 a′ at the initial thickness T₀. Thistrimming step reduces the resonant frequency of the first BAW resonator720 a. In particular, the first trimming step has reduced the thicknessof the central region 754 a′ of the upper electrode 750 a of the firstBAW resonator 720 a by a thickness of ΔT₁. This first trimming step,however, has not been applied to the upper electrode 750 b of the secondBAW resonator 720 b, which remains at the initial thickness T₀.

FIGS. 7E and 7F are cross-sections of the BAW resonators 720 a and 720b, respectively, after a second trimming step. In contrast to the firsttrimming step, which was applied only to the first BAW resonator 720 a,the second trimming step is applied to both of the BAW resonators 720 aand 720 b. The zoomed in view of FIG. 7F shows that the second trimmingstep has reduced the thickness of the central region 754 b′ of the upperelectrode 750 b of the second BAW resonator 720 b by a thickness of ΔT₂.This reduces the thickness of the central region 754 b′ of the upperelectrode 750 b of the second BAW resonator 720 b to a final thicknessof T_(F2).

The zoomed in view of FIG. 7E shows that the second trimming step hasreduced the thickness of the central region 754 a″ of the upperelectrode 750 a of the first BAW resonator 720 a by an additionalthickness of ΔT₂. This reduces the thickness of the central region 754a″ of the upper electrode 750 a of the second BAW resonator 720 a to afinal thickness of T_(F1), where T_(F1) differs from the initialthickness T₀ of the upper electrode 750 a by the sum of ΔT₁ and ΔT₂.

FIG. 8 is a flow diagram schematically illustrating certain steps in aprocess 800 for trimming two BAW resonators on a single substrateincluding a shared trimming step in an embodiment. The cross sections ofFIGS. 7A to 7F can correspond to the stages of the process 800. Theprocess 800 begins at a stage 805 where a die is provided supporting afirst BAW resonator and a second BAW resonator. In some embodiments, thefirst and second BAW resonators may form parts of first and secondfilters, respectively, where both filters are supported by the singledie. These first and second BAW resonators may be provided with anuntrimmed upper electrode, for example, as illustrated in FIGS. 7A and7B. Alternatively, the first and second BAW resonators may be providedwith central regions having thicknesses thinner than the thickness ofsurrounding raised frame regions.

The process 800 moves to a stage 810 where a first trimming step hasbeen used to selectively trim the first BAW resonator without trimmingthe second BAW resonator. This selective trimming step may reduce thethickness of a central region of the first BAW resonator by a desiredthickness, or may otherwise adjust a dimension of a portion of the upperelectrode of the first BAW resonator. FIGS. 7C and 7D illustrate anexample of the first and second BAW resonators after the first trimmingstep.

The process 800 moves to a stage 815 where a second trimming step hasbeen used to trim both the first BAW resonator and the second BAWresonator. This second trimming step may reduce the thickness of centralregions of both the first BAW resonator and the second BAW resonator bya desired thickness, or may otherwise adjust a dimension of portions ofthe upper electrodes of the first and second BAW resonators. The secondtrimming step can trim the thicknesses of the upper electrodes in theactive regions of the first and second BAW resonators by approximatelythe same amount. FIGS. 7E and 7F illustrate an example of the first andsecond BAW resonators after the second trimming step. The steps of theprocess 800 can be performed in any suitable order. For example, theshared trimming step can be performed before a trimming step for one ofthe two resonators in certain instances.

Additional trimming steps not explicitly described herein may be used totrim these BAW resonators and/or additional BAW resonators notexplicitly described with respect to process 800. In some embodiments,the orders of the first and second trimming steps may be reversed. Afterall trimming steps have been performed, a packaging process may beperformed to form a package encapsulating the die, which includes thetrimmed BAW resonators, in a single package.

In the embodiments described with respect to FIGS. 7A to 8, two trimmingsteps are used, and two different final thicknesses are provided. Inother embodiments, additional manufacturing efficiencies can be achievedwhen larger numbers of BAW resonators are trimmed on a single substrate.

FIGS. 9A through 9I illustrate cross-sections of a portion of three BAWresonators at various stages of a manufacturing process including twoshared trimming steps according to another embodiment. FIG. 9A shows across-section of a first BAW resonator 920 a including an upperelectrode 950 a overlying a portion of a piezoelectric layer 930 a, aswell as a detail view of a portion of the upper electrode 950 a. FIG. 9Bshows a cross-section of a second BAW resonator 920 b including an upperelectrode 950 b overlying a portion of a piezoelectric layer 930 b, aswell as a detail view of a portion of the upper electrode 950 b. FIG. 9Cshows a cross-section of a third BAW resonator 920 c including an upperelectrode 950 c overlying a portion of a piezoelectric layer 930 c, aswell as a detail view of a portion of the upper electrode 950 c.

FIGS. 9D to 9F are cross-sections of the BAW resonators 920 a, 920 b,and 920 c, respectively, after a first shared trimming step. As shown inFIG. 9D, the first shared trimming step reduces the thickness of acentral region 954 a′ of the upper electrode 950 a of the first BAWresonator 920 a, while leaving the thickness of a frame region of theupper electrode 950 a surrounding the central region 954 a′ at theinitial thickness T₀. Similarly, FIG. 9E shows that the first sharedtrimming step reduces the thickness of a central region 954 b′ of theupper electrode 950 b of the second BAW resonator 920 b, while leavingthe thickness of a frame region of the upper electrode 950 b surroundingthe central region 954 b′ at the initial thickness T₀. This firsttrimming step, however, has not been applied to the upper electrode 950c of the third BAW resonator 920 c, which remains at the initialthickness T₀, as shown in FIG. 9F.

FIGS. 9G to 9I are cross-sections of the BAW resonators 920 a, 920 b,and 920 c, respectively, after a second shared trimming step. Incontrast to the first trimming step, which was applied to the first BAWresonator 920 a and the second BAW resonator 920 b, the second trimmingstep is applied to the first BAW resonator 920 a and the third BAWresonator 920 c. The zoomed in view of FIG. 9I shows that the secondtrimming step reduces the thickness of the central region 954 c′ of theupper electrode 950 c of the third BAW resonator 920 c by a thickness ofΔT₂. This reduces the thickness of the central region 954 c′ of theupper electrode 950 c of the second BAW resonator 920 c to a finalthickness of T_(F3).

The zoomed in view of FIG. 9G shows that the second trimming step hasreduced the thickness of the central region 954 a″ of the upperelectrode 950 a of the first BAW resonator 920 a by an additionalthickness of ΔT₂. This reduces the thickness of the central region 954a″ of the upper electrode 950 a of the second BAW resonator 920 a to afinal thickness of T_(F1), where T_(F1) differs from the initialthickness T₀ of the upper electrode 950 a by the sum of ΔT₁ and ΔT₂.

Because the second trimming step has not affected the second BAWresonator 920 b, the thickness of the central region 954 b′ of the upperelectrode 950 b of the second BAW resonator 920 b remains at a finalthickness of T_(F2), where T_(F2) differs from the initial thickness T₀of the upper electrode 950 b by the thickness of ΔT₁. The processillustrated in FIGS. 9A to 9I has, using only two shared trimming steps,formed BAW resonators having three different final thicknesses T_(F1),T_(F2), and T_(F3).

This efficiency is possible because the overall trimming of first BAWresonator 920 a can be defined as a sum of the trimming to be applied tothe second and third BAW resonators 920 b and 920 c. With increasednumbers of resonators on a single substrate, there is an increasedlikelihood that an overall amount of trimming for a given resonator canbe defined in terms of a combination of trimming steps to be applied toone or more other resonators.

FIG. 10 is a flow diagram schematically illustrating certain steps in aprocess 1000 for trimming three BAW resonators on a single substrateincluding two shared trimming steps in another embodiment. The crosssections of FIGS. 9A to 9I can correspond to the stages of the process1000. The process 1000 begins at a stage 1005 where a die is providedsupporting first, second, and third BAW resonators. In some embodiments,these three BAW resonators may be included in two different filters on asingle die. The two filters can include other BAW resonators on thesingle die. In certain instances, three BAW resonators on the single diecan be included in three different filters. The first, second, and thirdBAW resonators may be provided with an untrimmed upper electrode, asillustrated in FIGS. 9A to 9C, or they may be provided with centralregions having thicknesses thinner than the thickness of surroundingframe regions.

The process 1000 moves to a stage 1010 where a first trimming step hasbeen used to selectively trim the first and second BAW resonatorswithout trimming the third BAW resonator. This selective trimming stepmay reduce the thicknesses of central regions of the first and secondBAW resonators by a desired thickness, or may otherwise adjustdimensions of portions of the upper electrodes of the first and secondBAW resonators. FIGS. 9D to 9F illustrate an example of the first,second, and third BAW resonators after the first trimming step.

The process 1000 moves to a stage 1015 where a second trimming step hasbeen used to selectively trim both the first and third BAW resonatorswithout further trimming the second BAW resonator. This second trimmingstep may reduce the thickness of central regions of both the first BAWresonator and the third BAW resonator by a desired thickness, or mayotherwise adjust a dimension of portions of the upper electrodes of thefirst and third BAW resonators. FIGS. 9G to 9I illustrate an example ofthe first, second, and third BAW resonators after the second trimmingstep. The steps of the process 1000 can be performed in any suitableorder.

Additional trimming steps not explicitly described herein may be used totrim these resonators and/or additional resonators not explicitlydescribed with respect to process 1000. In some embodiments, the ordersof the first and second trimming steps may be reversed. After alltrimming steps have been performed, a packaging process may be performedto form a package encapsulating the die, which includes the trimmed BAWresonators, in a single package.

FIG. 11A is a top plan view schematically illustrating two BAW filters,each including a plurality of BAW resonators according to an embodiment.The illustrated first BAW filter 1100 a and the second BAW filter 1100 bare shown as standalone filters. These filters can alternatively beincluded in a multiplexer, such as a duplexer, and be electricallycoupled to each other at a common node of the multiplexer.

The first BAW filter 1100 a includes four series BAW resonators 1120_(S1), 1120 _(S2), 1120 _(S3), and 1120 _(S4), and three shunt BAWresonators 1120 _(P1), 1120 _(P2), and 1120 _(P3). One or more of thefour series BAW resonators 1120 _(S1), 1120 _(S2), 1120 _(S3), and 1120_(S4) can have a first resonant frequency f₁, and the remainder of theseries BAW resonators can have a second resonant frequency f₂. One ormore of the three shunt BAW resonators 1120 _(P1), 1120 _(P2), and 1120_(P3) can have a third resonant frequency f₃, and the remainder of theshunt BAW resonators can have a fourth resonant frequency f₄.

Similarly, the second BAW filter 1100 b also includes four series BAWresonators 1160 _(S1), 1160 _(S2), 1160 _(S3), and 1160 _(S4), and threeshunt BAW resonators 1160 _(P1), 1160 _(P2), and 1160 _(P3). One or moreof the four series BAW resonators 1160 _(S1), 1160 _(S2), 1160 _(S3),and 1160 _(S4) can have a fifth resonant frequency f₅, and the remainderof the series BAW resonators can have a sixth resonant frequency f₆. Oneor more of the three shunt BAW resonators 1160 _(P1), 1160 _(P2), and1160 _(P3) can have a seventh resonant frequency f₇, and the remainderof the shunt BAW resonators can have an eighth resonant frequency f₈.

If the first and second BAW filters 1100 a and 1100 b were formed onseparate substrates, the formation of each of first and second BAWfilters 1100 a and 1100 b would each involve at least 3 trimming steps.This would result in a total of at least 6 trimming steps to form thefirst and second BAW filters 1100 a and 1100 b, even when at least someof the resonant frequencies of BAW resonators of the first BAW filter1100 a and the second BAW filter 1100 b are the same.

In contrast, if the first and second BAW filters 1100 a and 1100 b areformed on a common substrate of a multi-filter die, the first and secondBAW filters 1100 a and 1100 b can include BAW resonators with at leastsome shared resonant frequencies and/or can include BAW resonators withat least some common resonant frequency differentials, such that sharedtrimming steps can be used to reduce the overall number of trimmingsteps to form both filters.

In one embodiment, the first and second BAW filters 1100 a and 1100 bcan be designed such that one of the series resonator resonantfrequencies is shared between the first and second BAW filters 1100 aand 1100 b, and both of the shunt resonator resonant frequencies areshared between the first and second BAW filters 1100 a and 1100 b. Insuch an embodiment, the second frequency f₂ may be equal to the sixthfrequency f₆, the third frequency f₃ may be equal to the seventhfrequency f₇, and the fourth frequency f₄ may be equal to the eighthfrequency f₈. In such an embodiment, four trimming steps may be used toform the first and second BAW filters 1100 a and 1100 b. These steps areillustrated in Table 1, in which bold text is used to designate BAWresonators trimmed during a given trimming step and asterisks

are used to designate the point at which a BAW resonator has beentrimmed to its final resonant frequency. Each trimming step can shift anresonant frequency of a BAW resonator by a different amount. Forexample, each of the trimming steps can shift the resonant frequency bya different amount in a range from about 10 megahertz (MHz) to 100 MHzin certain embodiments.

TABLE 1 Resonator Start Trim 1 Trim 2 Trim 3 Trim 4 1120 _(S1)

 f₁ f₁ f₁ f₁ f₁ 1120 _(S2) f₁ f₁ f₁

 f ₂ f₂ 1120 _(S3)

 f₁ f₁ f₁ f₁ f₁ 1120 _(S4) f₁ f₁ f₁

 f ₂ f₂ 1120 _(P1) f₁

 f ₃ f₃ f₃ f₃ 1120 _(P2) f₁ f ₃ f₃ f₃

 f ₄ 1120 _(P3) f₁

 f ₃ f₃ f₃ f₃ 1160 _(S1) f₁ f₁

 f ₅ f₅ f₅ 1160 _(S2) f₁ f₁ f₁

 f ₂ f₂ 1160 _(S3) f₁ f₁ f₁

 f ₂ f₂ 1160 _(S4) f₁ f₁

 f ₅ f₅ f₅ 1160 _(P1) f₁

 f ₃ f₃ f₃ f₃ 1160 _(P2) f₁

 f ₃ f₃ f₃ f₃ 1160 _(P3) f₁ f ₃ f₃ f₃

 f ₄

The BAW resonators of the BAW filters 1100 a and 1100 b may be formedwith an initial resonant frequency f₁, which corresponds to the finalresonant frequency of series resonators 1120 _(S1) and 1120 _(S3) offirst BAW filter 1100 a. No further trimming of series resonators 1120_(S1) and 1120 _(S3) of first BAW filter 1100 a is desired, and notrimming steps will be applied to these resonators.

The first trimming step may be a shared trimming step which is appliedto resonators of both the first and second BAW filters 1100 a and 1100b. In this embodiment, the first trimming step is applied to all of theshunt BAW resonators 1120 _(P1), 1120 _(P2), and 1120 _(P3) of first BAWfilter 1100 a to all of the shunt BAW resonators 1160 _(P1), 1160 _(P2),and 1160 _(P3) of second BAW filter 1100 b, to adjust the resonantfrequency of these shunt resonators from f₁ to f₃. This resonantfrequency f₃ corresponds to the final resonant frequency of shuntresonators 1120 _(P1) and 1120 _(P3) of first BAW filter 1100 a andshunt resonators 1160 _(P1) and 1160 _(P2) of second BAW filter 1100 b,and no further trimming steps will be applied to these resonators.

The second trimming step is applied only to series BAW resonators 1160_(S1) and 1160 _(S4) of second BAW filter 1100 b, and adjusts theresonant frequency of these series resonators from f₁ to their finalresonant frequency of f₅.

The third trimming step is another shared trimming step applied toseries BAW resonators 1120 _(S2) and 1120 _(S4) of first BAW filter 1100a and to series BAW resonators 1160 _(S2) and 1160 _(S3) of second BAWfilter 1100 b to adjust the resonant frequency of these seriesresonators from f₁ to their final resonant frequency of f₅.

The fourth trimming step is another shared trimming step applied toshunt BAW resonator 1120 _(P2) of first BAW filter 1100 a and to shuntBAW resonator 1160 _(P3) of second BAW filter 1100 b. This trimming stepadjusts the resonant frequency of shunt BAW resonator 1120 _(P2) offirst BAW filter 1100 a and shunt BAW resonator 1160 _(P3) of second BAWfilter 1100 b from f₃ to their final resonant frequency of f₄.

In this embodiment, the shunt BAW resonator 1120 _(P2) of first BAWresonator 1100 a and the shunt BAW resonator 1160 _(P3) of second BAWfilter 1100 b are the only resonators exposed to multiple trimmingsteps, although in other embodiments, more or fewer resonators may beexposed to multiple trimming steps. Although identified as first throughfourth trimming steps, the various trimming steps may in otherembodiments be performed in any suitable order.

FIG. 11B is a top plan view schematically illustrating two BAW filtersthat are co-packaged and that each have a BAW resonators with the sameresonant frequency. In FIG. 11B, BAW filters 1100 a′ and 1100 b′ areco-packaged within a single package 1170. The BAW filters 1100 a′ and1100 b′ can include any suitable combination of features of the BAWfilters 1100 a and 1100 b of FIG. 11A. BAW resonators of the BAW filters1100 a′ and 1100 b′ can be trimmed with any suitable combination offeatures discussed with reference to Table 1 and/or Table 2. A packagingarea 1174 surrounding the BAW filters 1100 a′ and 1100 b′ need notextend between the two filters 1100 a′ and 1100 b′, which should reducethe overall size of the package 1170 in comparison to separatelypackaging filters 1100 a′ and 1100 b′.

FIG. 11B shows a zoomed in views of a first area 1172 a of the firstfilter 1100 a′ and a second area 1172 b of the second filter 1100 b′.The first area 1172 a and the second area 1172 b are on the same area ofa common substrate of a multi-filter die. In the first area 1172 a, thefirst filter 1100 a′ includes the BAW resonator 1120 _(P1). In thesecond area 1172 b, the second filter 1100 b′ includes the BAW resonator1160 _(P1). As illustrated, the BAW resonators 1120 _(P1) and 1160 _(P1)are FBARs. As also illustrated, the BAW resonators 1120 _(P1) and 1160_(P1) each include a raised frame structure. The BAW resonators 1120_(P1) and 1160 _(P1) can include a common material stack.

The BAW resonators 1120 _(P1) and 1160 _(P1) can have the same resonantfrequencies as each other. The resonant frequencies of the BAWresonators 1120 _(P1) and 1160 _(P1) can differ by no more than aprocessing variation associated with forming and trimming the BAWresonators 1120 _(P1) and 1160 _(P1). The BAW resonators 1120 _(P1) and1160 _(P1) can have the resonant frequencies within 1 MHz of each other.The BAW resonators 1120 _(P1) and 1160 _(P1) can have the resonantfrequencies within 0.5 MHz of each other. Two BAW resonators ofdifferent filters on a common multi-filter die can be located in anysuitable area of the multi-filter die. In certain instances, three ormore BAW resonators of at least two different filters on a commonmulti-filter die can have the same resonant frequency. The BAWresonators 1120 _(P1) and 1160 _(P1) having upper electrodes with thesame thickness can contribute to these resonators having the sameresonant frequencies. As used herein, the phrase “the same resonantfrequency” is intended to encompass having exactly the same resonantfrequency and to also encompass having resonant frequencies that varywithin a processing variation associated with forming and trimming theBAW resonators.

In one particular embodiment, the resonators of BAW filters 1100 a and1100 b may have an initial resonant frequency of 2366 MHz. The firsttrimming step may reduce the resonant frequency of the affectedresonators by 97 MHz. The second trimming step may reduce the resonantfrequency of the affected resonators by 15 MHz. The third trimming stepmay reduce the resonant frequency of the affected resonators by 29 MHz.The fourth trimming step may reduce the resonant frequency of theaffected resonators by 19 MHz. In this example, each trimming stepreduces the resonant frequency of the affected resonators. Table 2illustrates the change in frequency at each step of this embodiment, inwhich bold text is used to designate BAW resonators trimmed during agiven trimming step and asterisks

are used to designate the point at which a BAW resonator has beentrimmed to its final resonant frequency.

TABLE 2 Trim 1 Trim 2 Trim 3 Trim 4 Resonator Start (−97 MHz) (−15 MHz)(−29 MHz) (−19 MHz) 1120 _(S1)

 2366 2366 2366 2366 2366 1120 _(S2) 2366 2366 2366

 2337 2337 1120 _(S3)

 2366 2366 2366 2366 2366 1120 _(S4) 2366 2366 2366

 2337 2337 1120 _(P1) 2366

 2269 2269 2269 2269 1120 _(P2) 2366 2269 2269 2269

 2250 1120 _(P3) 2366

 2269 2269 2269 2269 1160 _(S1) 2366 2366

 2351 2351 2351 1160 _(S2) 2366 2366 2366

 2337 2337 1160 _(S3) 2366 2366 2366

 2337 2337 1160 _(S4) 2366 2366

 2351 2351 2351 1160 _(P1) 2366

 2269 2269 2269 2269 1160 _(P2) 2366

 2269 2269 2269 2269 1160 _(P3) 2366 2269 2269 2269

 2250

In another embodiment, the first and second BAW filters 1100 a and 1100b can be designed such that, despite having no resonant frequencies ofBAW resonators in common, certain frequency differentials are sharedbetween BAW resonators of each of the two filters 1100 a and 1100 b. Forexample, the filters 1100 a and 1100 b can be designed such that thedifference between the series resonator resonant frequencies of filter1100 a (f₁−f₂) is equal to the difference between the series resonatorresonant frequencies of filter 1100 b (f₅−f₆), and the differencebetween the shunt resonator resonant frequencies of filter 1100 a(f₃−f₄) is equal to the difference between the shunt resonator resonantfrequencies of filter 1100 b (f₇−f₈). In particular, these resonantfrequencies may be designed such that the same trimming step whichshifts the resonant frequency of a resonator from f₁ to f₂ will alsoshift the resonant frequency of another resonator from f₅ to f₆, andthat the same trimming step which shifts the resonant frequency of aresonator from f₃ to f₄ will also shift the resonant frequency ofanother resonator from f₇ to f₈.

In such an embodiment, five trimming steps may be used to form the firstand second BAW filters 1100 a and 1100 b. These steps are illustrated inTable 2, in which bold text is used to designate BAW resonators trimmedduring a given trimming step and asterisks

are used to designate the point at which a BAW resonator has beentrimmed to its final resonant frequency.

TABLE 3 Resonator Start Trim 1 Trim 2 Trim 3 Trim 4 Trim 5 1120 _(S1)

 f₁ f₁ f₁ f₁ f₁ f₁ 1120 _(S2) f₁ f₁ f₁

 f ₂ f₂ f₂ 1120 _(S3)

 f₁ f₁ f₁ f₁ f1 f₁ 1120 _(S4) f₁ f₁ f₁

 f ₂ f₂ f₂ 1120 _(P1) f₁

 f ₃ f₃ f₃ f₃ f₃ 1120 _(P2) f₁ f ₃ f₃ f₃ f₃

 f ₄ 1120 _(P3) f₁

 f ₃ f₃ f₃ f₃ f₃ 1160 _(S1) f₁ f₁

 f ₅ f₅ f₅ f₅ 1160 _(S2) f₁ f₁ f ₅

 f ₆ f₅ f₆ 1160 _(S3) f₁ f₁ f ₅

 f ₆ f₅ f₆ 1160 _(S4) f₁ f₁

 f ₅ f₅ f₅ f₅ 1160 _(P1) f₁ f₃ f₃ f₃

 f ₇ f₇ 1160 _(P2) f₁ f₃ f₃ f₃

 f ₇ f₇ 1160 _(P3) f₁ f₃ f₃ f₃ f ₇

 f ₈

The BAW resonators of the BAW filters 1100 a and 1100 b may be formedwith an initial resonant frequency f₁, which corresponds to the finalresonant frequency of series resonators 1120 _(S1) and 1120 _(S3) offirst BAW filter 1100 a. No further trimming of series resonators 1120_(S1) and 1120 _(S3) of first BAW filter 1100 a is desired, and notrimming steps will be applied to these resonators.

The first trimming step may be a shared trimming step which is appliedto resonators of both the first and second BAW filter 1100 a and 1100 b.In this embodiment, the first trimming step is applied to all of theshunt BAW resonators 1120 _(P1,) 1120 _(P2), and 1120 _(P3) of first BAWfilter 1100 a and to all of the shunt BAW resonators 1160 _(P1), 1160_(P2), and 1160 _(P3) of second BAW filter 1100 b, to adjust theresonant frequency of these shunt resonators from f₁ to f₃. Thisresonant frequency f₃ corresponds to the final resonant frequency ofshunt resonators 1120 _(P1) and 1120 _(P3) of first BAW filter 1100 a,and no further trimming steps will be applied to these resonators.

The second trimming step is applied only to the series BAW resonators1160 _(S1), 1160 _(S2), 1160 _(S3), and 1160 _(S4) of second BAW filter1100 b, and adjusts the resonant frequency of these series resonatorsfrom f₁ to an resonant frequency of f₅. For series BAW resonators 1160_(S1), and 1160 _(S4) of second BAW filter 1100 b, the resonantfrequency of f₅ corresponds to the final resonant frequency, and nofurther trimming steps will be applied to these resonators.

The third trimming step is another shared trimming step applied toseries BAW resonators 1120 _(S2) and 1120 _(S4) of first BAW filter 1100a and to series BAW resonators 1160 _(S2) and 1160 _(S3) of second BAWfilter 1100 b to adjust the resonant frequency of these seriesresonators. This trimming step adjusts the resonant frequency of seriesBAW resonators 1120 _(S2) and 1120 _(S4) of first BAW filter 1100 a fromf₁ to their final resonant frequency of f₂. As the series BAW resonators1160 _(S2) and 1160 _(S3) of second BAW filter 1100 b have already beentrimmed in the second trimming step, the resonant frequency of theseries BAW resonators 1160 _(S2) and 1160 _(S3) of second BAW filter1100 b is instead adjusted from f₅ to their final resonant frequency off₆. No further trimming steps will be applied to these resonators.

The fourth trimming step is applied only to the shunt BAW resonators1160 _(P1), 1160 _(P2), and 1160 _(P3) of second BAW filter 1100 b. Thistrimming step adjusts the resonant frequency of shunt BAW resonators1160 _(P1), 1160 _(P2), and 1160 _(P3) of second BAW filter 1100 b fromf₃ to f₇. For shunt BAW resonators 1160 _(P1) and 1160 _(P2), f₇represents their final resonant frequency, and no further trimming stepswill be applied.

The fifth trimming step is another shared trimming step applied to shuntBAW resonator 1120 _(P2) of first BAW filter 1100 a and to shunt BAWresonator 1160 _(P3) of second BAW filter 1100 b Like the third trimmingstep described above, this fifth trimming step again applies a sharedtrimming step to resonators of two different frequencies. This trimmingstep adjusts the resonant frequency of shunt BAW resonator 1120 _(P2) offirst BAW filter 1100 a from f₃ to its final resonant frequency of f₄,and adjusts the shunt BAW resonator 1160 _(P3) of second BAW filter 1100b from f₇ to its final resonant frequency of f₈.

In this embodiment, three shared trimming steps are applied toresonators of both filters, and two filters have been formed, each ofwhich have 4 distinct BAW resonator resonant frequencies representingeight total unique BAW resonator resonant frequencies. A reduction intrimming steps from 6 to 5 has been achieved, even though neither of thefilters share a common resonator resonant frequency with the otherfilter. Although identified as first through fifth trimming steps, thevarious trimming steps may in other embodiments be performed in anysuitable order, and more or fewer resonators may be exposed to multipletrimming steps.

In this embodiment, the shunt BAW resonator 1120 _(P2) of first BAWfilter 1100 a and the shunt BAW resonator 1160 _(P3) of second BAWfilter 1100 b are the only resonators exposed to multiple trimmingsteps, although in other embodiments, more or fewer resonators may beexposed to multiple trimming steps.

FIG. 11C is a top plan view schematically illustrating two BAW filtersthat are co-packaged and that each have two BAW resonators with the samedifferential in resonant frequency. In FIG. 11C, BAW filters 1100 a″ and1100 b″ are co-packaged within a single package 1180. The BAW filters1100 a″ and 1100 b″ can include any suitable combination of features ofthe BAW filters 1100 a and 1100 b of FIG. 11A. BAW resonators of the BAWfilters 1100 a″ and 1100 b″ can be trimmed with any suitable combinationof features discussed with reference to Table 3 and/or Table 4. Anysuitable combination of features discussed with reference to FIG. 11Bcan be combined with any suitable combination of features discussed withreference to FIG. 11C. A packaging area 1184 surrounding the BAW filters1100 a″ and 1100 b″ need not extend between the two filters 1100 a″ and1100 b″, which should reduce the overall size of the package 1180 incomparison to separately packaging filters 1100 a″ and 1100 b″.

FIG. 11C shows a zoomed in views of a first area 1182 a 1 and a secondarea 1182 a 2 of the first filter 1100 a″ and a third area 1182 b 1 anda fourth area 1182 b 2 of the second filter 1100 b″. The first to fourthareas 1182 a 1, 1182 a 2, 1182 b 1, 1182 b 2 are on the same area of acommon substrate of a multi-filter die. In the first area 1182 a 1, thefirst filter 1100 a″ includes the BAW resonator 1120 _(S1). In thesecond area 1182 a 1, the first filter 1100 a″ includes the BAWresonator 1120 _(S2). In the third area 1182 b 1, the second filter 1100b″ includes the BAW resonator 1160 _(S1). In the fourth area 1182 b 2,the second filter 1100 b″ includes the BAW resonator 1160 _(S2).

As illustrated, the BAW resonators 1120 _(S1), 1120 _(S2), 1160 _(S1),and 1160 _(S2) are FBARs. As also illustrated, the BAW resonators 1120_(S1), 1120 _(S2), 1160 _(S1), and 1160 _(S2) each include a raisedframe structure. The BAW resonators 1120 _(S1), 1120 _(S2), 1160 _(S1),and 1160 _(S2) can include a common material stack.

A difference between resonant frequencies of the BAW resonators 1120_(S1) and 1120 _(S2) of the first filter 1100 a″ is approximately equalto a difference between resonant frequencies of the BAW resonators 1160_(S1) and 1160 _(S2) of the second filter 1100 b″. The difference inresonant frequencies of the BAW resonators 1120 _(S1) and 1120 _(S2) andthe difference in resonant frequencies of the BAW resonators 1160 _(S1)and 1160 _(S2) can differ by no more than an amount associated withprocessing variation associated with forming and trimming these BAWresonators. The difference between resonant frequencies of the BAWresonators 1120 _(S1) and 1120 _(S2) can be within 1% of the differencebetween resonant frequencies of the BAW resonators 1160 _(S1) and 1160_(S2). The difference between resonant frequencies of the BAW resonators1120 _(S1) and 1120 _(S2) can be within 2% of the difference betweenresonant frequencies of the BAW resonators 1160 _(S1) and 1160 _(S2).The BAW resonators of different filters on a common multi-filter die canbe located in any suitable area of the multi-filter die. In certaininstances, three or more groups of two BAW resonators of at least twodifferent filters on a common multi-filter die can have the samedifference is resonant frequencies as each other. The differences inresonant frequencies can correspond to differences in thickness of upperelectrodes in a central portion of an active area of the BAW resonators.As used herein, the phrase “equal to a difference between resonantfrequencies” is intended to encompass having exactly the same differencebetween resonant frequencies and to also encompass having a differencebetween resonant frequencies within processing variation associated withforming and trimming the BAW resonators.

In one particular embodiment, the resonators of BAW filters 1100 a and1100 b may have an initial resonant frequency of 2366 MHz. The firsttrimming step may reduce the resonant frequency of the affectedresonators by 97 MHz. The second trimming step may reduce the resonantfrequency of the affected resonators by 15 MHz. The third trimming stepmay reduce the resonant frequency of the affected resonators by 29 MHz.The fourth trimming step may reduce the resonant frequency of theaffected resonators by 9 MHz. The fifth trimming step may reduce theresonant frequency of the affected resonators by 19 MHz. Table 4illustrates the change in frequency at each step of this embodiment, inwhich bold text is used to designate BAW resonators trimmed during agiven trimming step and asterisks

are used to designate the point at which a BAW resonator has beentrimmed to its final resonant frequency.

TABLE 4 Trim 1 Trim 2 Trim 3 Trim 4 Trim 5 Resonator Start (−97 MHz)(−15 MHz) (−29 MHz) (−9 MHz) (−19 MHz) 1120 _(S1)

 2366 2366 2366 2366 2366 2366 1120 _(S2) 2366 2366 2366

 2337 2337 2337 1120 _(S3)

 2366 2366 2366 2366 2366 2366 1120 _(S4) 2366 2366 2366

 2337 2337 2337 1120 _(P1) 2366

 2269 2269 2269 2269 2269 1120 _(P2) 2366 2269 2269 2269 2269

 2250 1120 _(P3) 2366

 2269 2269 2269 2269 2269 1160 _(S1) 2366 2366

 2351 2351 2351 2351 1160 _(S2) 2366 2366 2351

 2322 2322 2322 1160 _(S3) 2366 2366 2351

 2322 2322 2322 1160 _(S4) 2366 2366

 2351 2351 2351 2351 1160 _(P1) 2366 2269 2269 2269

 2260 2260 1160 _(P2) 2366 2269 2269 2269

 2260 2230 1160 _(P3) 2366 2269 2269 2269 2260

 2241

In the above example, the frequency change caused by a trimming processis substantially constant, even when the layers being trimmed are atdifferent initial thicknesses prior to the performance of that trimmingstep. However, depending on the nature of the layer stack being trimmed,and the thickness of the trimmed layer relative to the amount beingtrimmed, the relationship between trim depth and frequency change may benon-linear.

In such an embodiment, a given trimming process applied to two layers ofdifferent thicknesses may result in a frequency change for one layerwhich is different than the frequency change for the other layer. Insuch embodiments, filters on a single substrate may still be designedsuch that shared trimming processes can be used to form the filters,even though the exact frequency changes resulting from those trimmingprocesses may be different in different filters.

Multi-filter substrates having a plurality of BAW filters can bepackaged as described above with respect to FIGS. 3A to 4C, or using anyother suitable packaging process. In some embodiments, acoustic waveresonators of other types, such as SAW resonators and/or Lamb waveresonators, may also be co-packaged with one or more BAW filters.

FIG. 12 is a schematic diagram of a radio frequency module 1200 thatincludes a bulk acoustic wave component 1076 according to an embodiment.The illustrated radio frequency module 1200 includes the BAW component1076 and other circuitry 1077. The BAW component 1076 can include BAWfilters with any suitable combination of features of the BAW filtersdisclosed herein. The BAW component 1076 can include a BAW die thatincludes BAW resonators of multiple filters.

The BAW component 1076 shown in FIG. 12 includes filters 1078 andterminals 1079A and 1079B. The filters 1078 includes BAW resonators, andmay be co-packaged with another filter including BAW resonators, or withanother acoustic wave resonator in accordance with any suitableprinciples and advantages disclosed herein. The terminals 1079A and1078B can serve, for example, as an input contact and an output contact,and may be in electrical communication with a conductive structureextending through a laser-etched via. The BAW component 1076 and theother circuitry 1077 are on or supported by a common packaging substrate1080 in FIG. 12. The package substrate 1080 can be a laminate substrate.The terminals 1079A and 1079B can be electrically connected to contacts1081A and 1081B, respectively, on or supported by the packagingsubstrate 1080 by way of electrical connectors 1082A and 1082B,respectively. The electrical connectors 1082A and 1082B can be bumps orwire bonds, for example. The other circuitry 1077 can include anysuitable additional circuitry. For example, the other circuitry caninclude one or more one or more power amplifiers, one or more radiofrequency switches, one or more additional filters, one or more lownoise amplifiers, the like, or any suitable combination thereof. Theradio frequency module 1200 can include one or more packaging structuresto, for example, provide protection and/or facilitate easier handling ofthe radio frequency module 1200. Such a packaging structure can includean overmold structure formed over the packaging substrate 1200. Theovermold structure can encapsulate some or all of the components of theradio frequency module 1200.

FIG. 13 is a schematic diagram of a radio frequency module 1300 thatincludes a bulk acoustic wave component according to an embodiment. Asillustrated, the radio frequency module 1300 includes duplexers 1185A to1185N that include respective transmit filters 1186A1 to 1186N1 andrespective receive filters 1186A2 to 1186N2, a power amplifier 1187, aselect switch 1188, and an antenna switch 1189. The radio frequencymodule 1300 can include a package that encloses the illustratedelements. The illustrated elements can be disposed on a common packagingsubstrate 1180. The packaging substrate can be a laminate substrate, forexample.

The duplexers 1185A to 1185N can each include two acoustic wave filterscoupled to a common node. The two acoustic wave filters can be atransmit filter and a receive filter, and may be co-packaged with oneanother. As illustrated, the transmit filter and the receive filter caneach be band pass filters arranged to filter a radio frequency signal.One or more of the transmit filters 1186A1 to 1186N1 can include one ormore BAW filters in accordance with any suitable principles andadvantages disclosed herein. Similarly, one or more of the receivefilters 1186A2 to 1186N2 can include one or more BAW filters inaccordance with any suitable principles and advantages disclosed herein.Although FIG. 13 illustrates duplexers, any suitable principles andadvantages disclosed herein can be implemented in other multiplexers(e.g., quadplexers, hexaplexers, octoplexers, etc.) and/or inswitch-plexers.

The power amplifier 1187 can amplify a radio frequency signal. Theillustrated switch 1188 is a multi-throw radio frequency switch. Theswitch 1188 can electrically couple an output of the power amplifier1187 to a selected transmit filter of the transmit filters 1186A1 to1186N1. In some instances, the switch 1188 can electrically connect theoutput of the power amplifier 1187 to more than one of the transmitfilters 1186A1 to 1186N1. The antenna switch 1189 can selectively couplea signal from one or more of the duplexers 1185A to 1185N to an antennaport ANT. The duplexers 1185A to 1185N can be associated with differentfrequency bands and/or different modes of operation (e.g., differentpower modes, different signaling modes, etc.).

FIG. 14A is a schematic block diagram of a module 1210 that includes apower amplifier 1212, a radio frequency switch 1214, and duplexers 1291Ato 1291N in accordance with one or more embodiments. The power amplifier1212 can amplify a radio frequency signal. The radio frequency switch1214 can be a multi-throw radio frequency switch. The radio frequencyswitch 1214 can electrically couple an output of the power amplifier1212 to a selected transmit filter of the duplexers 1291A to 1291N. Oneor more filters of the duplexers 1291A to 1291N can include any suitablenumber of bulk acoustic wave resonators, in accordance with any suitableprinciples and advantages discussed herein, and some or all of thefilters may be co-packaged as discussed above. Any suitable number ofduplexers 1291A to 1291N can be implemented.

FIG. 14B is a schematic block diagram of a module 1270 that includesfilters 1271A to 1271N, a radio frequency switch 1274, and a low noiseamplifier 1272 according to an embodiment. One or more filters of thefilters 1271A to 1271N can include any suitable number of bulk acousticwave resonators, in accordance with any suitable principles andadvantages discussed herein, and some or all of the filters may beco-packaged as discussed above. Any suitable number of filters 1271A to1271N can be implemented. The illustrated filters 1271A to 1271N arereceive filters. In some embodiments (not illustrated), one or more ofthe filters 1271A to 1271N can be included in a multiplexer that alsoincludes a transmit filter. The radio frequency switch 1274 can be amulti-throw radio frequency switch. The radio frequency switch 1274 canelectrically couple an output of a selected filter of filters 1271A to1271N to the low noise amplifier 1272. In some embodiments (notillustrated), a plurality of low noise amplifiers can be implemented.The module 1270 can include diversity receive features in certainapplications.

FIG. 15 is a schematic block diagram of a module 1395 that includesduplexers 1391A to 1391N and an antenna switch 1394. One or more filtersof the duplexers 1391A to 1391N can be co-packaged with one another andmay include any suitable number of bulk acoustic wave resonators, inaccordance with any suitable principles and advantages discussed herein.Any suitable number of duplexers 1391A to 1391N can be implemented. Theantenna switch 1394 can have a number of throws corresponding to thenumber of duplexers 1391A to 1391N. The antenna switch 1394 canelectrically couple a selected duplexer to an antenna port of the module1395.

FIG. 16A is a schematic diagram of a wireless communication device 1400that includes filters 1403 in a radio frequency front end 1402 accordingto an embodiment. The filters 1403 can include BAW resonators of two ormore filters in accordance with any suitable principles and advantagesdiscussed herein. The wireless communication device 1400 can be anysuitable wireless communication device. For instance, a wirelesscommunication device 1400 can be a mobile phone, such as a smart phone.As illustrated, the wireless communication device 1400 includes anantenna 1401, an RF front end 1402, a transceiver 1404, a processor1405, a memory 1406, and a user interface 1407. The antenna 1401 cantransmit RF signals provided by the RF front end 1402. Such RF signalscan include carrier aggregation signals. Although not illustrated, thewireless communication device 1400 can include a microphone and aspeaker in certain applications.

The RF front end 1402 can include one or more power amplifiers, one ormore low noise amplifiers, one or more RF switches, one or more receivefilters, one or more transmit filters, one or more duplex filters, oneor more multiplexers, one or more frequency multiplexing circuits, thelike, or any suitable combination thereof. The RF front end 1402 cantransmit and receive RF signals associated with any suitablecommunication standards. The filters 1403 may be co-packaged with oneanother, or with a subset of the filters 1403, and can include BAWresonators including any suitable combination of features discussed withreference to any embodiments discussed above.

The transceiver 1404 can provide RF signals to the RF front end 1402 foramplification and/or other processing. The transceiver 1404 can alsoprocess an RF signal provided by a low noise amplifier of the RF frontend 1402. The transceiver 1404 is in communication with the processor1405. The processor 1405 can be a baseband processor. The processor 1405can provide any suitable base band processing functions for the wirelesscommunication device 1400. The memory 1406 can be accessed by theprocessor 1405. The memory 1406 can store any suitable data for thewireless communication device 1400. The user interface 1407 can be anysuitable user interface, such as a display with touch screencapabilities.

FIG. 16B is a schematic diagram of a wireless communication device 1510that includes filters 1503 in a radio frequency front end 1502 andsecond filters 1513 in a diversity receive module 1512. The wirelesscommunication device 1510 is like the wireless communication device 1400of FIG. 16A, except that the wireless communication device 1520 alsoincludes diversity receive features. As illustrated in FIG. 16B, thewireless communication device 1520 includes a diversity antenna 1511, adiversity module 1512 configured to process signals received by thediversity antenna 1511 and including filters 1513, and a transceiver1504 in communication with both the radio frequency front end 1502 andthe diversity receive module 1512. The filters 1513 may be co-packagedwith one another, or with a subset of the filters 1513, and can includeBAW resonators including any suitable combination of features discussedwith reference to any embodiments discussed above.

Acoustic wave resonators disclosed herein can be included in a filterarranged to filter a radio frequency signal. One or more acoustic waveresonators including any suitable combination of features disclosedherein be included in a filter arranged to filter a radio frequencysignal in a fifth generation (5G) New Radio (NR) operating band withinFrequency Range 1 (FR1). A filter arranged to filter a radio frequencysignal in a 5G NR operating band can include BAW resonators disclosedherein. FR1 can be from 410 megahertz (MHz) to 7.125 gigahertz (GHz),for example, as specified in a current 5G NR specification. One or moreacoustic wave resonators in accordance with any suitable principles andadvantages disclosed herein can be included in a filter arranged tofilter a radio frequency signal in a fourth generation (4G) Long TermEvolution (LTE) operating band. One or more acoustic wave resonators inaccordance with any suitable principles and advantages disclosed hereincan be included in a filter having a passband that includes a 4G LTEoperating band and a 5G NR operating band.

Any of the embodiments described above can be implemented in mobiledevices such as cellular handsets. The principles and advantages of theembodiments can be used for any systems or apparatus, such as any uplinkcellular device, that could benefit from any of the embodimentsdescribed herein. The teachings herein are applicable to a variety ofsystems. Although this disclosure includes some example embodiments, theteachings described herein can be applied to a variety of structures.Any of the principles and advantages discussed herein can be implementedin association with RF circuits configured to process signals having afrequency in a range from about 30 kHz to 300 GHz, such as a frequencyin a range from about 410 MHz to 8.5 GHz.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as die and/or acoustic wave filter assembliesand/or packaged radio frequency modules, uplink wireless communicationdevices, wireless communication infrastructure, electronic testequipment, etc. Examples of the electronic devices can include, but arenot limited to, a mobile phone such as a smart phone, a wearablecomputing device such as a smart watch or an ear piece, a telephone, atelevision, a computer monitor, a computer, a modem, a hand-heldcomputer, a laptop computer, a tablet computer, a personal digitalassistant (PDA), a microwave, a refrigerator, an automobile, a stereosystem, a DVD player, a CD player, a digital music player such as an MP3player, a radio, a camcorder, a camera, a digital camera, a portablememory chip, a washer, a dryer, a washer/dryer, a peripheral device, awrist watch, a clock, etc. Further, the electronic devices can includeunfinished products.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,”“include,” “including” and the like are to be construed in an inclusivesense, as opposed to an exclusive or exhaustive sense; that is to say,in the sense of “including, but not limited to.” The word “coupled”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Likewise, the word “connected”, as generally used herein,refers to two or more elements that may be either directly connected, orconnected by way of one or more intermediate elements. Additionally, thewords “herein,” “above,” “below,” and words of similar import, when usedin this application, shall refer to this application as a whole and notto any particular portions of this application. Where the contextpermits, words in the above Detailed Description using the singular orplural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel apparatus, methods, andsystems described herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the disclosure. For example, while blocks arepresented in a given arrangement, alternative embodiments may performsimilar functionalities with different components and/or circuittopologies, and some blocks may be deleted, moved, added, subdivided,combined, and/or modified. Each of these blocks may be implemented in avariety of different ways. Any suitable combination of the elements andacts of the various embodiments described above can be combined toprovide further embodiments. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure.

What is claimed is:
 1. A multi-filter die with bulk acoustic wavefilters, the multi-filter die comprising: a first filter located in afirst region of a substrate, the first filter including a firstplurality of bulk acoustic wave resonators; and a second filter locatedin a second region of the substrate, the second filter including asecond plurality of bulk acoustic wave resonators, at least one of thefirst plurality of bulk acoustic wave resonators having the sameresonant frequency as at least one of the second plurality of bulkacoustic wave resonators.
 2. The multi-filter die of claim 1 wherein thefirst and second filters are included in a multiplexer.
 3. Themulti-filter die of claim 2 wherein the first and second filters areelectrically connected to one another at a common contact by at leastone electrical connection of the multi-filter die.
 4. The multi-filterdie of claim 1 wherein the multi-filter die is free from electricalconnections between the first filter and the second filter.
 5. Themulti-filter die of claim 1 wherein the first plurality of bulk acousticwave resonators and the second plurality of bulk acoustic waveresonators are film bulk acoustic wave resonators.
 6. The multi-filterdie of claim 1 wherein the first plurality of bulk acoustic waveresonators each include a raised frame structure.
 7. The multi-filterdie of claim 1 wherein the first filter is a first band pass filterhaving a first passband, the second filter is a second band pass filterhaving a second passband, and the first passband overlaps with thesecond passband.
 8. The multi-filter die of claim 1 wherein the firstfilter and the second filter include a common material stack.
 9. Themulti-filter die of claim 1 wherein a thickness of a piezoelectric layerof the one of the first plurality of bulk acoustic wave resonators isthe same as a thickness of a piezoelectric layer of the one of thesecond plurality of bulk acoustic wave resonators.
 10. The multi-filterdie of claim 1 wherein a thickness of a lower electrode of the one ofthe first plurality of bulk acoustic wave resonators is the same as athickness of a lower electrode of the one of the second plurality ofbulk acoustic wave resonators.
 11. The multi-filter die of claim 10wherein the lower electrode of the one of the first plurality of bulkacoustic wave resonators includes a same material as the lower electrodeof the one of the second plurality of bulk acoustic wave resonators. 12.A multi-filter die with bulk acoustic wave filters, the multi-filter diecomprising: a first filter located in a first region of a substrate, thefirst filter including a first plurality of bulk acoustic waveresonators, each of the first plurality of bulk acoustic wave resonatorshaving a resonant frequency; and a second filter located in a secondregion of the substrate, the second filter including a second pluralityof bulk acoustic wave resonators, each of the second plurality of bulkacoustic wave resonators having a resonant frequency, a differencebetween resonant frequencies of two bulk acoustic wave resonators of thefirst plurality of bulk acoustic wave resonators being equal to adifference between resonant frequencies of two bulk acoustic waveresonators of the second plurality of bulk acoustic wave resonators. 13.The multi-filter die of claim 12 wherein each of the resonantfrequencies of the first plurality of bulk acoustic wave resonators aredifferent from each of the resonant frequencies of the second pluralityof bulk acoustic wave resonators.
 14. The multi-filter die of claim 12wherein the first and second filters are included in a multiplexer. 15.The multi-filter die of claim 12 wherein the multi-filter die is freefrom electrical connections between the first filter and the secondfilter.
 16. The multi-filter die of claim 12 wherein the first pluralityof bulk acoustic wave resonators and the second plurality of bulkacoustic wave resonators are film bulk acoustic wave resonators.
 17. Themulti-filter die of claim 12 wherein the first plurality of bulkacoustic wave resonators each include a raised frame structure.
 18. Themulti-filter die of claim 12 wherein the first filter is a first bandpass filter having a first passband, the second filter is a second bandpass filter having a second passband, and the first passband overlapswith the second passband.
 19. The multi-filter die of claim 12 whereinthe first filter and the second filter are formed using a commonmaterial stack.
 20. A radio frequency system comprising: a radiofrequency amplifier; a multi-filter die including a first filter in afirst region of a substrate and a second filter in a second region ofthe substrate, the first filter including a first plurality of bulkacoustic wave resonators, the second filter including a second pluralityof bulk acoustic wave resonators, at least one of the first plurality ofbulk acoustic wave resonators having the same resonant frequency as atleast one of the second plurality of bulk acoustic wave resonators; anda switch configured to selectively electrically connect the radiofrequency amplifier and the first filter.